Igor de Paiva Affonso

The impact of a dam on the helminth fauna and health of a neotropical fish species Salminus brasiliensis (Cuvier 1816) from the upper Paraná River, Brazil.

The aim of the present study was to detect changes in the structure of the helminth parasite infracommunities in Salminus brasiliensis (Cuvier 1816) from the floodplain of the upper Paraná River after construction of the Porto Primavera Hydroelectric Plant. A total of 126 fish in the period before the dams construction and 56 specimens 10 years after this event were analysed. Three species of parasites were collected before the construction of the dam: Prosthenhystera obesa Diesing, 1850 (Digenea), Cladocystis intestinalis Vaz, 1932 (Digenea) and Monticellia coryphicephala Monticelli, 1892 (Cestoda), and one nematode species in the larval stage, whose identification was not possible. After dam construction, the following helminth parasites were found: C. intestinalis, M. coryphicephala, Octospiniferoides incognita, Contracaecum spp. larvae and Contracaecum sp. type 2 larvae Moravec, Kohn & Fernandes 1993. The diversity of helminth parasites measured by the Brillouin diversity index (HB) differed significantly between the pre- and post-dam periods (mean HB = 0.069 and HB = 0.2, respectively; P= 0.0479; Mann-Whitney U test). The parasite community of S. brasiliensis before the construction of the dam showed concentration of dominance (C) of P. obesa (C = 0.38), while there was no concentration of dominance of any species of parasite (C = 0.22) after the dams construction. Before the Porto Primavera dam the relative condition factor of fish was 1.0; after the dams construction it was 0.93 (P < 0.0001; Mann-Whitney U test). This study records the disappearance of the species P. obesa and suggests that there has been local extinction of this parasite. The results show that the anthropic influence on natural systems is interfering with the welfare and health of S. brasiliensis, reflected by its fauna of helminth parasites.

Predation on Frogs by the Introduced Crab Dilocarcinus pagei Stimpson, 1861 (Decapoda, Trichodactylidae) on a Neotropical Floodplain

In general, amphibians are numerous and small-sized, and the gregarious behaviour of most species in the breeding season makes them potential prey for many different predators (Duellman & Trueb, 1994). Most predation occurs near or in the water (Toledo, 2005) in the breeding season, when the majority of species enter the water and consequently become accessible to potential aquatic predators (Bastos et al., 1994; Haddad & Bastos, 1997; Toledo, 2003). Among these predators are several species of freshwater and forest crabs, which can predate on the tadpoles (Gray & Christy, 2000) and frogs (Hayes, 1983), or at least mutilate their limbs or digits (Duellman & Trueb, 1994; Gray et al., 2002). Freshwater crabs are important organisms in food webs of tropical environments, where they act as detritivores or primary and secondary consumers, and can become either predators on, or prey for, other invertebrates (Hayes, 1983; Dobson et al., 2002; Marijnissen et al., 2009; Klaus & Plath, 2011). Sublethal attacks normally occur when the predators are similar in size to, or smaller than, their prey (Schoener, 1979). Gray et al. (2002) stated that the most likely cause of injuries in frogs is attack by invertebrates such as ants, crabs, or spiders, which are neither prey nor predators but share the same habitat. The extensive floodplain of the Upper Paraná River contains many smaller rivers, canals, lakes and ponds, and wetlands, where a common feature is the presence of large patches of macrophytes (Pelicice et al., 2008). Macrophytes provide amphibians with shelter and refuge, but they also increase the incidence of predators (Denton & Beebee, 1997; Laurila, 1998), such as the crab Dilocarcinus pagei Stimpson, 1862 (cf. Magalhães et al., 2005).

Amphibia, Anura, Leptodactylidae, Leptodactylus mystaceus (Spix, 1824): distribution extension

This study presents the first record of Leptodactylus mystaceus at the Municipality of Maringa, Parana state, and its first occurrence at the South Region of Brazil, indicating the expansion of its geographic distribution.

Nesting patterns among Neotropical species assemblages: can reserves in urban areas be failing to protect anurans?

Nestedness among species assemblages implies that sites of lower species richness are subsets of richer sites in a regional species pool. This nestedness is a reflection of a non-random process of species loss as a consequence of factors that promote the disaggregation of assemblages. The impoverishment of assemblage diversity is more often observed in fragmented landscapes. This non-random process has important implications for conservation. We recorded 95 species of anurans across 22 protected areas, of which 11 sites were in an urban matrix and 11 were in a non-urban matrix. We found that sites in the urban matrix had lower richness and high values of nestedness with no spatial autocorrelation among geographic distances and species composition. Thus, species were non-randomly distributed across the landscape and a nested pattern was documented from non-urban matrix sites to urban matrix sites. The impoverishment of assemblages toward the urban matrix sites may suggest that protected areas in an urban matrix are less suitable for anuran conservation than those in a non-urban matrix sites. Both the ecological revitalization of protected areas in urban matrix and protection of non-urban forested sites are needed for the conservation of Neotropical anurans.

Cumulative ecological effects of a Neotropical reservoir cascade across multiple assemblages

Dams have altered the physiography and ecology of large rivers, causing severe environmental changes at a global scale. Assuming that series of reservoirs induce physical, chemical, and biological longitudinal changes in rivers, we tested the hypotheses that (i) the structure of biological communities in reservoir cascades is not only affected by changes in water quality, but also by cumulative hydrological alteration and impacts on river connectivity; and (ii) fish are more affected by cumulative effects of reservoirs when compared to other aquatic assemblages. Samplings of three assemblages (phytoplankton, benthic macroinvertebrates, and fish) were conducted in the reservoir cascade of São Francisco River, Brazil. We estimated the relative role of environmental and spatial predictors through variation partitioning analyses. Environmental variables, cumulative reservoir volume, longitudinal position, and distances from nearest reservoirs were used as explanatory variables. Environmental variables were the most important for the phytoplankton community. No significant effects of the predictors used were found for benthic macroinvertebrates, whereas spatial variables and cumulative reservoir volume were the most important predictors for fish. Therefore, our results provide evidence of impacts along reservoir cascades, and suggest that their effects mainly influence fish assemblages.